WiMAX is a telecommunications technology that applies for wireless transmission of data using a variety of transmission modes, from point-to-point links to portable internet access. The technology provides up to 75 Mb/sec symmetric broadband speed without requiring the use of cables. The technology is based on the IEEE 802.16 standard, also called Broadband Wireless Access and is described as a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL.
In a fixed wireless configuration, the WiMAX can replace (or supplement) the telephone company's copper wire networks and the cable TV's coaxial cable infrastructure, while offering Internet Service Provider (ISP) services. In its mobile variant, WiMAX has the potential to replace cellular networks.
WiMAX provides fixed, portable or mobile non-line-of sight service from a base station to a subscriber station, also known as customer premise equipment (CPE). One of the goals that were set for WiMAX, is, a radius of service coverage of 6 miles from a WiMAX base station for point-to-multipoint, non-line-of-sight service. This service should deliver approximately 40 megabits per second (Mbps) for fixed and portable access applications. WiMAX cell site may offer from one base station enough bandwidth to support hundreds of businesses with T1 speeds and thousands of residential customers with the equivalent of DSL services.
Mobile WiMAX takes the fixed wireless application a step further and enables cell phone-like applications on a much larger scale. For example, mobile WiMAX enables streaming video to be broadcast from a speeding platform (e.g. a police or other emergency vehicle at over 70 MPH). In addition to being the final leg in a quadruple play, it offers superior building penetration and improved security measures over fixed WiMAX. Mobile WiMAX will be very valuable for emerging services such as mobile TV and gaming. In addition, the WiMAX may allow its subscribers to receive a broad range of information services through their CPEs such as Internet access, VoIP, IPTV, in a two-way or interactive service.
There are two typical scenarios for a wireless deployment, point-to-point and point-to-multipoint. Point to point is used where there are two points of interest: one sender and one receiver. This is also a scenario for backhaul or the transport from the data source (data center, co-lo facility, fiber POP, Central Office, etc) to the subscriber or for a point for distribution using point to multipoint architecture. Backhaul radios are an industry of their own within the wireless industry. As architecture calls for a highly focused beam between two points range and throughput of point-to point radios will be higher than that of point-to-multipoint products. In a point-to-multipoint configuration, one base station can service hundreds of dissimilar subscribers in terms of bandwidth and services offered.
GRE tunnels are designed to be completely stateless. This means that each tunnel end-point does not keep any information about the state or availability of the remote tunnel end-point. Consequently, the local tunnel end-point router does not have the ability to bring the line protocol of the GRE tunnel interface down if the remote end-point is unreachable. The ability to mark an interface as being down when the remote end of the link is not available, is used in order to remove any routes (specifically static routes) in the routing table that use that interface as the outbound interface. Specifically, if the line protocol for an interface is changed to “down” state, any static routes that point out that interface would be removed from the routing table. Normally, a GRE tunnel interface comes up as soon as it is configured and stays up as long as there is a valid tunnel source address or interface which is up. The tunnel destination IP address must also be routable. This is true even if the other side of the tunnel has not been configured. This means that a static route or PBR forwarding of packets via the GRE tunnel interface remains in effect even though the GRE tunnel packets do not reach the other end of the tunnel.